On the bubble

Posted by Renee on May 04, 2007

Does anyone know about "on the bubble?" I'm guessing that the image is of a spirit level. Any insight into when or how the phrase entered everyday speech as meaning something like "could go either way" or "up in the air"? There's a poker usage that seems a little different: poker.about.com/ od/pokerglossary/g/bubble.htm